Providing a test capability in the network elements (NEs) of a transport network involves offering transport network operators a mechanism with which to observe, diagnose, isolate, and fix problems with the individual circuits associated with the transport network. A key attribute of this test capability is that it must enable access to a given end-to-end circuit without requiring the customer premises equipment (CPE) devices to be disconnected from their respective NE ports for the purpose of connecting test devices. In order to provide this test capability, digital cross-connect system (DCS) NEs include ports known as test access ports (TAPs). These TAPs are used to mirror the data flows at the various network interfaces. Thus, the DCSs integrate digital test access unit (DTAU) functions into the NEs themselves. The TAPs are connected to test units (TUs) for the purpose of monitoring the data flows, and may be used to inject traffic either towards an end-user or towards interior NEs within the transport network.
Various standards specify two distinct types of TAPs: (1) local TAPs and (2) remote TAPs. The local TAPs are used for connecting test devices to a NE and diagnosing circuits on that same NE. The remote TAPs, on the other hand, are connected to remote test units (RTUs). These RTUs are termed “remote” only because they are physically separated from the test operations systems (TOSs) that are used for testing. In all other aspects, local TAPs and remote TAPs are functionally equivalent. The TOSs communicate with a test system controller (TSC)/RTU via a control link to initiate test access. The standards do not specify the type of connection between the TSC and the RTU.
Disadvantageously, conventional remote test access features require manual cross-connects to be set up at every node that is needed to complete the network connection between the remote test set and the circuit of interest. This requires the transport network operator to login to every node and set up the cross-connect. If there is any traffic degradation or failure at any of the connection termination points (CTPs), there is no protection mechanism for the remote tap, and, as a result, the remote tap is not able to reach the circuit of interest. If it is desired to use the same remote tap to reach different circuits of interest using the same remote test set, all of the cross-connects that are set up must be torn down, and set up again. If the circuit of interest is modified, as in the case of protecting it or making it drop-and-continue, the remote tap is lost. Finally, the remote tap is inherently bidirectional. As a result, monitor modes are not supported.
Thus, what are needed are systems and methods for the implementation of a remote test access feature using VCPs and SNCs by the merge-and-split of flexible cross-connects, thereby addressing the disadvantages described above.